1. Field of the Invention
The present invention relates to the recovery of liquids and gas from subterranean formations and, more particularly, to the recovery of liquids and gas through a well in a manner to prevent liquid-loading of the well.
2. Setting of the Invention
It is critically important in the economic recovery of liquids and gas from a well to ensure that these fluids are recovered with the least expenditure of energy possible. Further, it is extremely advantageous to recover these fluids in a generally uniform flow rate to not overload and underload downstream fluid processing systems. Many of the wells used for recovering liquids and gas are capable of recovering liquids and gas to the surface with the assistance of the natural energy stored within the subterranean formation. When these fluids from the subterranean formation are recovered through a well, the pressure at the bottom of the well is reduced and additional dissolved gas comes out of solution and is recovered with other fluids. Although many wells will produce such fluids with a fairly uniform daily flow rate, the flow rate of each fluid that enters the well adjacent to the subterranean formation may fluctuate considerably. Even if the flow rate of each fluid into the well is fairly uniform, the undissolved gas is not uniformly distributed in the liquids entering the well. As is most often the case, much of the gas that has separated from the other liquids causes a constantly varying ratio of gas and liquids to enter the well. This non-uniform entry of fluids into the well not only adversely affects the pressure drop of the fluids at this point of entry, but also causes undesirable flow variations as the fluids move up to the surface. Accumulations or slugs of liquid can reduce the flow rate or even prevent fluids from being recovered from the well when the fluid head is greater than the natural energy stored within the subterranean formation.
It is very common for wells that produce a relatively low volume of fluid to "load up", i.e. become incapable of naturally producing fluids therefrom, or flow at a much reduced rate. If a well has become liquid loaded, then artificial lift systems need to be employed, such as rod pumping units, downhole electric submergible pumps or positive displacement pumps. All of these require an undesired use of energy to run such equipment. As an alternative, gas lift systems may be used if sufficient gas is present. An example of using such gas lift systems in horizontal wells is disclosed in the June 1992 American Oil and Gas Reporter, "Gas Lift Usage Can Increase Horizontal Well Production" by Byron Sandel, pages 45-47. While such gas lift systems provide the very desirable benefits of low cost as compared to pumping units, they still cannot overcome the above-described liquid loading problem.
There is a need for a simple and effective method of recovering liquids and gas from a subterranean formation in a manner to prevent liquid loading of the well.